Terminalia arjuna back powder (400 mg/kg,po) significantly reduced formalin-indued paw oedema at 24 h but not carrageenan-induced paw oedema. It significantly increased the anti-SRBC antibody titre in the secondary phase of immune response. The same dose significantly reduced the duration of licks and bites in both phases of formalin-induced pain response and showed significant increase in tail flick latency at higher dose (800mg/kg,po). These effects of T.arjuna were antagonised by pretreatment with naloxone (1mg/kg,ip). In another series of experiments, mice pretreated with morphine for three days in increasing doses (10, 15, 20 mg/kg, ip; twice daily) showed a decreased response in antinociceptive activity of morphine (5 mg/kg, ip). Further, cross tolerance was observed with T.arjuna (800mg/kg, po) in morphine tolerant animals. These findings support the hypothesis that T.arjuna has anti-inflammatory potential against some phlogistic agents along with some immunomodulatory activity and also has antinococeptive action probably mediated via central opioid receptors.